Business Loop I-90 - Deer Lodge

Business Loop I-90 through the Powell County seat of Deer Lodge follows Old U.S. 10 along Main Street. The entire 3.05 mile long route is also Montana Secondary Highway 275, though that route is unsigned.

The Deer Lodge business loop arcs west from Interstate 90 at Exit 185 and Sam Beck Road. Old U.S. 10 ties into Main Street from N Frontage Road, where Business Loop I-90 curves south. Main Street continues to Grant-Kohrs Ranch National Historic Site, the Deer Lodge city center, and the Old Montana Prison & Auto Museum. The east end is at a wye interchange (Exit 187) with Interstate 90 between the BNSF Railroad and Clark Fork river.

East

The lone reassurance marker for Business Loop I-90 eastbound stands along Main Street at Village Lane, just west of I-90.
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Main Street curves south and becomes part of Old U.S. 10 beyond N Frontage Road. Deer Lodge Mountain lines the western horizon.
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An array of businesses line Main Street south of Grant-Kohrs Ranch National Historic Site and Johnson Creek.
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Deer Lodge City Hall is on the southwest corner of Main Street and Cottonwood Avenue.
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Main Street south at Missouri Avenue in Downtown Deer Lodge.
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The lone traffic light in Deer Lodge is at Main Street and Milwaukee Avenue. Milwaukee Avenue west onto Conley Lake Road is unsigned S-272.
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The Old Montana Prison & Auto Museum lines the west side of Business Loop I-90 between Pennsylvania Avenue and Conley Avenue.
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Business Loop I-90 transitions into a rural highway south from Conley Avenue on the return to Interstate 90.
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The east end of Business Loop I-90 is a partial access interchange with no entrance ramp onto I-90 westbound.
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I-90 east trailblazer posted south after Valley View Drive.
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Crossing the Clark Fork river.
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Old U.S. 10 separates from Business Loop I-90 along S Frontage Road.
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The end of Business Loop I-90 along Main Street defaults onto eastbound Interstate 90 beyond the intersection with S Frontage Road.
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West

S Frontage Road (Old U.S. 10) ties into Business Loop I-90 (Main Street) just north of the exchange at Exit 187.
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Business Loop I-90 (Main Street) proceeds north along Old U.S. 10 to cross the Clark Fork river.
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Main Street expands to a commercial boulevard north from Conley Avenue into the city of Deer Lodge.
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Main Street north at Texas Street and the Old Montana Prison & Auto Museum.
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The Old Montana Prison & Auto Museum occupies three blocks along the west side of Business Loop I-90 (Main Street).
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Main Street north at Montana Avenue and Downtown Deer Lodge.
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Milwaukee Avenue is S-272 west 2.02 miles past Deer Lodge-City-County Airport (38S) to Golf Course Road.
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Main Street north at Missouri Avenue.
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Interstate 90 trailblazer posted along Main Street north across from the Grant-Kohrs Ranch National Historic Site Visitor Center.
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Business Loop I-90 (Main Street) diverges east from Old U.S. 10 at N Frontage Road.
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The north end of Business Loop I-90 is a diamond interchange joining Main Street and Sam Beck Lane with Interstate 90.
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Interstate 90 encircles the east side of Deer Lodge south to Anaconda and Butte.
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Connect with:

Interstate 90

Page Updated Thursday January 29, 2026.